1. Field of the Invention
The present invention relates to a sheet supply apparatus for supplying record sheet to an image forming apparatus such as a stencil printing machine or the like, particularly to a sheet supply apparatus capable of adjusting print position of print sheet in the left and right direction even in sheet supply operation.
2. Description of the Related Art
An image forming apparatus for forming an image by using record sheet, for example, print sheet for general use, uses the print sheet by loading the print sheet on a sheet supply table. Particularly, in the case of a stencil printing machine, high speed printing can be carried out since the printing operation is carried out by mounting stencil sheet on a print drum at inside of the machine and rotating the print drum. In correspondence therewith, there is constructed a constitution in which a comparatively large number of sheets of print sheet are loaded on the sheet supply table and the large number of sheets of print sheet can continuously be supplied in a short period of time in correspondence with printing speed.
The sheet supply table is constituted such that print sheet disposed at sheet supply position on the topmost face is supplied to a print section at inside of the printing machine sheet by sheet. A scraper roller (sheet supply roller) of the sheet supply section is provided at the sheet supply position and print sheet can continuously be supplied to inside of the apparatus by rotating the scraper roller.
Further, there is constructed a constitution in which the sheet supply table is controlled to elevate in correspondence with supply of the print sheet and print sheet at the topmost face is always brought into contact with the scraper roller.
According to the print sheet, a position thereof in the left and right direction (width direction orthogonal to a transfer direction) is made variable in supplying the print sheet from the sheet supply table to the print section to thereby enable to move an image forming position in the left and right direction on the print sheet. For example, in the case of a stencil printing machine, by making variable a transfer position in the left and right direction of print sheet relative to the print drum, a contact position of the print sheet relative to an image position of stencil sheet mounted to the print drum can be made variable in the left and right direction and the image forming position on the print sheet can be moved in the left and right direction.
FIG. 8 is a perspective view showing a sheet supply apparatus. A sheet supply table 50 loaded with print sheet is provided with a dial 51 for moving the sheet supply table 50 in the left and right direction. By manually adjusting the dial 51, a screw shaft 52 is rotated, a nut portion 53 fixed to the sheet supply table 50 is moved in the left and right direction and the sheet supply table 50 is moved in the same direction. Thereby, an image forming position on print sheet P can be adjusted to move in the left and right direction.
Print sheet P at the topmost face loaded on the sheet supply table 50, is brought into contact with a scraper roller 57a of sheet supply means 57 provided above the sheet supply table 50 and the print sheet is supplied sheet by sheet from the topmost face to a print section by rotating the scraper roller 57a.
The sheet supply table 50 is constituted such that the sheet supply table 50 is controlled to elevate gradually in compliance with supply of the print sheet P and the topmost face of the print sheet P is always brought into contact with the scraper roller 57a and can be supplied to the print section.
However, according to the above-described constitution, the sheet supply table 50 can be moved in the left and right direction directly by operating the dial 51. Therefore, when the dial 51 is operated in the printing operation, the print sheet P is supplied in an oblique direction, wrinkle is produced in the print sheet P, or the print sheet P is folded, as a result, sheet supply jam is caused.
Further, the scraper roller 57a undergoes damage, which gives rise to deterioration in print function at an early stage.
In the meantime, it is conceivable to move the sheet supply table by electrical drive using a motor or the like in place of the manual operation. However, the above-described problem cannot be solved at all by a constitution in which the sheet supply table is moved in the left and right direction simply by power of the motor.